Method of manufacturing an ultra low dielectric layer

ABSTRACT

An article may include a structure including a patterned metal on a surface of a substrate, the patterned metal including metal features separated by gaps of an average dimension of less than about 1000 nm. A porous low dielectric constant material having a dielectric value of less than about 2.7 substantially occupies all gaps. An interface between the metal features and the porous low dielectric constant material may include less than about 0.1% by volume of voids. A method may include depositing a filling material including a silicon-based resin having a molecular weight of less than about 30,000 Da and a porogen having a molecular weight greater than about 400 Da onto a structure comprising a patterned metal. The deposited filling material may be subjected to a first thermal treatment to substantially fill all gaps, and subjected to a second thermal treatment and a UV radiation treatment.

BACKGROUND

The drive of the semiconductor industry to improve integrated chipperformance through scaling has led to the exponential growth of activedevices on a chip. The combination of increased device density andshrinking dimensions has led to an increase in the RC (resistance timescapacitance) signal delay in the back end of line (BEOL) interconnectwiring. In the past, this problem was addressed by the industry using athree-prong approach. First using alternative chip design, more levelsof wiring were added at the smallest wiring dimensions to decrease thesignal transit distances. Second, to reduce interconnect resistivity,aluminum was replaced with copper, a metal with ˜30% lower resistivity.Finally, capacitance was reduced by replacing the interconnect insulatorwith a lower dielectric constant material (low k) including theintroduction of porosity.

However, the continued drive to improve chip performance through devicescaling has led to additional challenges in the BEOL, specifically theincreased resistivity stemming from grain boundary scattering in the Cuwiring and damage to the porous low k material caused by patterning andintegration. To mitigate both problems an alternate integrationapproach, subtractive copper etch (sub-etch Cu) was developed to replacethe typical damascene integration flow.

FIG. 1 is a flowchart that illustrates a typical subtractive copperetching process. The technique of FIG. 1 starts from a blanket Cu filmdeposition, thus minimizing electron scattering, and creates Cu lineswith large crystals (>1 μm). FIGS. 2A-2D are conceptual diagramsillustrating successive lateral cross-sectional views of an articleprocessed by the technique of FIG. 1.

Step 110 includes forming at least one polish stop 240 on a surface ofan integrated circuit substrate 220. The at least one polish stop 240may assist in attaining a level plane in a subsequent polishing step,for example, chemical mechanical polishing. In some processes, thepolish stop 240 may include a material that is harder than the materialremoved during polishing, for example, metal that may be deposited onthe substrate 220 and then polished. Step 130 includes depositing themetal 260 over one or both of the surface of the integrated circuitsubstrate 220 and the at least one polish stop 240. The metal 260 mayinclude grain boundaries 262. Step 150 includes annealing the depositedmetal 260. Step 170 includes polishing the deposited metal 260. Step 190includes patterning the metal 260 to form metal interconnects 264.

SUMMARY

The metal interconnect lines 264 in FIG. 2D may be filled with ULKinterlayer dielectric (ILD) material after the patterning step. Damageto the ULK material that may be subsequently deposited over the metalpattern should be minimized, since the metal 260 is patterned ratherthan the ULK material itself as in a standard damascene approach.

However, successfully filling the metal interconnect lines 264 withULK-ILD material, for example, after the patterning (190), presents amajor challenge in the implementation of this alternative dual damascenesubtractive etch technique. The challenge of filling patterned metalinterconnect lines on integrated circuit substrates with defect-freeULK-ILD increases as the metal interconnect line dimensions, for examplethe average separation between metal interconnect lines, also known aspitch, is decreased, for instance, to 100 nanometers (nm) and below asprojected for subsequent technology nodes. Defects may result fromincomplete filling, resulting in separation between filling material andmetal interconnects, or from the generation of voids, for instance,within the filling material near metal interconnects or at interfacesbetween metal interconnects and filling materials. Example techniquesand articles described in this disclosure provide structures includinglow-defect or defect-free ULK-ILD filled metal patterns on substrates.

An example technique includes depositing a filling material onto astructure including a patterned metal on a surface of a substrate. Thepatterned metal includes metal features separated by gaps. The gaps mayhave an average gap dimension of less than about 1000 nm, for example,an average gap dimension of less than about 100 nm. The filling materialincludes a silicon-based resin having a molecular weight of less thanabout 30,000 Da and a porogen having a molecular weight greater thanabout 400 Da. The deposited filling material is subjected to apredetermined first thermal treatment to substantially fill all gapswith the filling material. The thermally treated deposited fillingmaterial is subjected to a second thermal treatment and a UV radiationtreatment, thereby crosslinking the silicon-based resin and decomposingthe porogen, to form a porous low dielectric constant material having adielectric value of less than about 2.7. An interface between the metalfeatures and the porous low dielectric constant material includes lessthan about 0.1% by volume of voids.

In another example, an article includes a structure including apatterned metal on a surface of a substrate. The patterned metalincludes metal features separated by gaps of an average dimension ofless than about 1000 nm. A porous low dielectric constant materialhaving a dielectric value of less than about 2.7 substantially occupiesall gaps. An interface between the metal features and the porous lowdielectric constant material includes less than about 0.1% by volume ofvoids.

The example techniques can be used for the defect free filling of metalinterconnect structures with a pitch of 100 nm or less using an ultralow dielectric constant material. In example techniques, the molecularweight (M_(wr)) of the resin material is selected to facilitate fullpenetration and stability upon curing. In examples, porosity may beintroduced using a pore generator (porogen) to arrive at low dielectricmaterials with predetermined dielectric constant (k) values, forexample, k<2.7, or even ultra-low dielectric (ULK) materials, forexample, k<2.0. A porogen may be an amphiphilic molecule that exhibits ahydrophilic-lipophilic balance (HLB) value. In examples, the porogen'smolecular weight (M_(wp)) and HLB value are selected to reduce defects.In examples, a combination UV/thermal curing of the resin-porogen hybridis used to form a fully cured ULK inter-layer dielectric (ULK-ILD)material that exhibits substantially reduced defects or is substantiallydefect free. For example, a substantially defect-free ULK-ILD materialmay include no voids or defects having a critical dimension greater than5 nm. Thus example articles may include substantially integratedcircuits including metal lines filled with substantially defect-freeULK-ILD material.

The details of one or more aspects of the invention are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other aspects of this invention are made more evidentin the following Detailed Description, when read in conjunction with theattached Drawing Figures, wherein:

FIG. 1 is a flowchart illustrating an example technique of subtractivecopper etching.

FIGS. 2A-2D are conceptual diagrams illustrating successive lateralcross-sectional views of an article processed by the example techniqueof FIG. 1.

FIGS. 3A-3C are conceptual lateral cross-sectional views of a structureincluding a patterned metal and a filling material.

FIG. 4 is a flow diagram illustrating an example technique for filling apatterned material with a filling material.

FIGS. 5A and 5B are scanning electron microscopy images of refilledmetal structures.

FIG. 6 is a chart illustrating a plot of the porogen's M_(wp) versusHLB, and the selected processing windows for defect free gap-fill of 80nm pitch metal structures.

FIGS. 7A and 7B are scanning electron microscopy images of refilledmetal structures.

It should be understood that features of certain Figures of thisdisclosure may not necessarily be drawn to scale, and that the Figurespresent non-exclusive examples of the techniques disclosed herein.

DETAILED DESCRIPTION

FIGS. 3A-3C are conceptual lateral cross-sectional views of a structureincluding a patterned metal and a filling material. As shown in FIG. 3A,article 300 includes a substrate 320. The substrate 320 may include asubstrate in an integrated circuit fabrication process, for example, awafer that can support structures subsequently fabricated on a surface.In various embodiments, which are not intended to be limiting, thesubstrate 320 includes at least one of silicon, metal oxide, or galliumarsenide. Article 300 may also include polish stops 340 on the surfaceof substrate 320 that may remain after metal patterning has beenperformed on substrate 320, for example, as described with reference toFIG. 1 above. Article 300 includes metal features 364 disposed on amajor surface of the substrate 320. The metal features 364 may includemetal interconnects, for example, metal interconnects including metal360. In an example, metal 360 includes a metal or alloy. For example,metal 360 may include copper, aluminum, or an alloy of copper oraluminum, or any other metal or alloy suitable for use in integratedchips. Metal features 364 may be formed by a subtractive metalpatterning technique including subtractive etching, for example, asdescribed above with reference to FIG. 1. For example, the metalfeatures 364 may be present in the form of metal interconnects onsubstrate 320, separated by gaps, as shown in FIG. 3A. The gaps may havean average gap dimension, for example, a gap length or separationdistance, of less than about 1000 nm. In examples, the average gapdimension of the gaps separating metal features 364 may be less thanabout 1000 nm, less than about 500 nm, less than about 300 nm, or lessthan about 100 nm. For example, the average gap dimension of the gapsseparating metal features 364 may be less than about 100 nm. The gapsmay be subsequently filled with a filling material, for example,dielectric material, as described below.

The patterned metal including metal features 364 on substrate 320 may befilled with a filling material 380. Initially, filling material 380 maybe deposited as a layer on the surface of substrate 320 presenting themetal features 364, as shown in FIG. 3A. The filling material 380 mayinclude a composition that forms a porous low dielectric constantmaterial on subsequent treatment, for example, thermal treatment andcuring. In examples, the filling material 380 may include a curable orcross-linkable resin, for example, organosilicate or siloxane, or anysuitable silicon-based resin. In various embodiments, the fillingmaterial 380 may include a low-molecular-weight thermosetting polymer,e.g., a soluble silsesquioxane dissolved in a suitable organic solvent.In various non-limiting examples, the silicon-based resin has amolecular weight of less than about 30,000 Daltons (Da), or less thanabout 20,000 Da, or less than about 10,000 Da, or less than about 5000Da, or about 3000 Da, or less than about 3000 Da.

The filling material 380 may include other components apart from adielectric-forming material. In some embodiments, the filling material380 includes an optional porogen, which in this application refers acomponent with appropriate thermal properties to act as a poregenerator. A porogen may include any chemical compound or species thatpromotes the formation of pores in a surrounding matrix. For example,the porogen may be sacrificial, and may decompose during or after poregeneration when subjected to predetermined conditions, such as one orboth of thermal treatment and UV radiation treatment.

In some embodiments, the porogen may include surfactants, or amphiphilicorganic compounds that contain hydrophilic groups (known as heads) andhydrophobic groups (known as tails). The balance between the size of theheads and the tails may be measured in terms of thehydrophilic-lipophilic balance (HLB) value. The HLB value may bedetermined using Griffin's method or Davies' method, and typicallyranges from 0 to 20, or even more than 20. The HLB value of a surfactantporogen may influence pore formation, for example, pore size. However,the HLB value can also influence other properties of compositions, forexample, void, gap or defect formation within the filling material 380or between the filling material 380 including the porogen and the metalfeatures 364.

In some embodiments, which are not intended to be limiting, the porogenincludes a surfactant or a suitable amphiphilic compound having apredetermined HLB value. Examples of suitable porogens include, but arenot limited to, one or more of polyoxyethylene fatty alcohols, sorbitanfatty acid esters, ethoxylated sorbitan fatty acid esters, orethoxylates, commercial embodiments of which include Brij, SPAN(Sigma-Aldrich), TWEEN (Sigma-Aldrich), or Tergitol (Dow ChemicalCompany) surfactants, including sorbitan monolaureate (SPAN 20),sorbitan monopalmitate (SPAN 40), sorbitan monostearate (SPAN 60),sorbitan tristearate (SPAN 65), sorbitan monooleate (SPAN 80), sorbitantrioleate (SPAN 85), PEG-20 sorbitan monolaureate (TWEEN 20), PEG-4sorbitan monolaureate (TWEEN 21), PEG-20 sorbitan monopalmitate (TWEEN40), PEG-20 sorbitan monostearate (TWEEN 60), PEG-4 sorbitanmonostearate (TWEEN 61), PEG-20 sorbitan tristearate (TWEEN 65), PEG-20sorbitan monooleate (TWEEN 80), polyoxyethylenesorbitan monooleate(TWEEN 81), polyoxyethylenesorbitan trioleate (TWEEN 85), polyethyleneglycol hexadecyl ether or polyoxyethylene (2) cetyl ether (Brij 52),polyoxyethylene (10) stearyl ether (Brij 76), polyoxyethylene (20)stearyl ether (Brij 78), polyethylene (100) stearyl ether (Brij 700),secondary alcohol ethoxylate (Tergitol 15-S-15), or other suitablesurfactants or combinations thereof.

In some non-limiting examples, the porogen may have an HLB value greaterthan about 2, greater than about 5, greater than about 10, greater thanabout 12, greater than about 15, or greater than about 16.

The molecular weight of the porogen may influence pore formation, forexample, pore size. However, the molecular weight of the porogen mayalso influence other properties of compositions, for example, void, gapor defect formation within the filling material 380 or between thefilling material 380 including the porogen and the metal features 364.In various embodiments, the porogen may have a molecular weight greaterthan about 300 Da, greater than about 400 Da, greater than about 700 Da,greater than about 1000 Da, or greater than about 4000 Da.

The porogen may be chosen based on its compatibility with the matrix orthe resin in filling material 380. For example, the porogen and theresin may be soluble or compatible in the form of a colloidal dispersionto yield optically transparent solutions. The porogen and resin may alsobe mutually compatible to produce uniform films or layers after spinningand optically transparent films after the first thermal treatment orhot-plate post-apply bake. The resin or matrix may also sufficientlystiffen or thicken prior to porogen decomposition to resist capillaryforces that may act to collapse pores during porogen decomposition.

In some embodiments, the filling material 380 may include about 75 to 85wt % of resin, and about 15 to 25 wt % of porogen. For example, thefilling material 380 may include at least about 75 wt %, 80 wt %, or 85wt % of resin and lower than or about 25 wt %, 20 wt %, or 15 wt % ofthe porogen. In examples, the filling material 380 may include less thanabout 75 wt % of the resin, for example, about 50 wt % of the resin, andabout 50 wt % of the porogen.

The filling material 380 may be deposited by dispensing or spin-oncoating to obtain a uniform coating or layer on substrate 320. Inexamples, spin-coating may include spin-coating the filling material 380on substrate 320 following by hot-plate baking, for example at 75 to250° C.

The filling material 380 may be subjected to a first thermal treatment,resulting in flow or penetration of the layer of filling material 380into the patterned metal, to occupy the gaps between the metal features364, as shown in FIG. 3B. In examples, the first thermal treatmentincludes heating the deposited filling material 380 to a temperaturefrom about 75° C. to about 250° C. for a time from about 1 minute toabout 30 minutes. Heat may be applied by a suitable controlled heatsource. While the first thermal treatment may be effective to result inflow or otherwise softening of the filling material 380 to allow thefilling material 380 to occupy the gaps between the metal features 364,in examples, the first thermal treatment may be controlled to avoidcuring or pore generation, for example, to avoid premature curing orpore generation within the filling material 380. In examples, the firstthermal treatment may initiate or promote subsequent curing or poregeneration.

In some embodiments, after the first thermal treatment, the thermallytreated filling material 380 may be subjected to a second thermaltreatment and a UV radiation treatment while occupying the gaps betweenthe metal features 364, as shown in FIG. 3C. In examples, one or both ofthe second thermal treatment or the UV radiation treatment may result incross-linking or curing of the filling material 380, for example, of asilicon-based resin in the filling material 380. A heat source may beused to provide heat for the second thermal treatment, and a UV sourcemay be used to generate UV radiation.

In some embodiments, the second thermal treatment includes heating thethermally treated filling material 380 to a temperature between about300° C. to about 500° C. for a time from about 30 minutes to about 120minutes. The second thermal treatment may include ramping up, rampingdown, or combinations thereof of the filling material between itsinitial temperature and a temperature between about 300° C. to about500° C.

In various embodiments, the UV radiation treatment includes subjectingthe thermally treated filling material 380 to UV radiation of wavelengthfrom 100 to 400 nm for a time of about 30 seconds to about 300 seconds.The UV radiation treatment may include exposing the filling material 380to broad wavelength UV, or varying the wavelength over the duration oftime. For example, a broad wavelength UV source may be a mercury bulbwith a peak wavelength at 365 nm and concentration of about 254 nm. Inone non-limiting example, the second thermal treatment includes heatingthe filling material to 400° C. while subjecting the filling material toa broad wavelength UV for 300 seconds.

In some embodiments, the second thermal treatment and the UV radiationtreatment may be simultaneous for at least a predetermined period oftime. In examples, the predetermined period of time may includesubstantially an entire duration of the second thermal treatment. Forexample, the filling material 380 may be subjected to UV radiationtreatment during the second thermal treatment, and additionally one orboth of before or after the completion of the second thermal treatment.In some embodiments, the predetermined period of time includessubstantially an entire duration of the UV radiation treatment. Forexample, the filling material 380 may be subjected to the second thermaltreatment during the UV radiation treatment, and additionally one orboth of before or after the completion of the UV radiation treatment. Insome embodiments, the second thermal treatment and the UV radiationtreatment may not be simultaneous, and one may follow the other. Inother embodiments, the second thermal treatment and the UV radiationtreatment may include multiple stages of interspersed, simultaneous, ornon-simultaneous phases or one or both of the second thermal treatmentand the UV radiation treatment.

In some embodiments, one or both of the second thermal treatment or theUV radiation treatment may result in one or both of pore formation andporogen decomposition, forming pores in the filling material 380 (notshown). For example, the pores formed may range in size from about 1 nmto about 5 nm. In examples, the curing may result in a reduction of thedeposited thickness of filling material 380, as shown in FIG. 3C.

The filling material 380 may form a porous low dielectric constantmaterial as a result of one or both of the second thermal treatment andthe UV radiation treatment. In examples, the porous low dielectricconstant material includes less than about 0.1% by volume, or less than0.01% by volume of voids. Voids may include non-pore voids formed atinterfaces between the filling material 380 and the metal features 364,or voids that are not formed by the porogen. For example, the lowdielectric constant material may be substantially free of voids having acritical void dimension greater than about 5 nm, or greater than about10 nm nm, or greater than about 100 nm. The critical void dimension maybe a maximum diameter, a maximum average diameter, a maximum axiallength, or a maximum axial length of a void. In examples, the lowdielectric constant material may be substantially free of voids, forexample, non-pore voids or voids not generated by the porogen.

FIG. 4 is a flow diagram illustrating an example technique for filling apatterned material with a filling material. The example technique mayinclude depositing a filling material onto a structure including apatterned metal on a surface of a substrate (420). The patterned metalmay include metal features separated by gaps, the gaps having an averagegap dimension of less than about 1000 nm. The filling material mayinclude a silicon-based resin having a molecular weight of less thanabout 30,000 Da and a porogen having a molecular weight greater thanabout 400 Da. The example technique may include subjecting the depositedfilling material to a first thermal treatment to substantially fill allgaps with the filling material (440). The example technique may includesubjecting the thermally treated deposited filling material to a secondthermal treatment and a UV radiation treatment, thereby crosslinking thesilicon-based resin and decomposing the porogen, to form a porous lowdielectric constant material having a dielectric value of less thanabout 2.7 (460). An interface between the metal features and the porouslow dielectric constant material includes less than about 0.1% by volumeof voids after one or both of the second thermal treatment and the UVradiation treatment.

Thus, example articles and techniques according to the disclosureprovide a structure including a patterned metal on a surface of asubstrate, the patterned metal including metal features separated bygaps of an average dimension of less than about 1000 nm, a porous lowdielectric constant material having a dielectric value of less thanabout 2.7 substantially occupying all gaps, such that an interfacebetween the metal features and the porous low dielectric constantmaterial may include less than about 0.1% by volume of voids.

The present disclosure will be illustrated by the following non-limitingexamples.

EXAMPLES Example 1

Example 1 presents the selection of molecular weight of Si-based ULKresin material to reduce or avoid the formation of defects. FIGS. 5A and5B are scanning electron microscopy images of refilled metal structures.As shown in FIG. 5A, using a ULK resin having M_(wr)=30,000 Da resultedin incomplete gap-fill, even when the pitch between metal structures wasas high as 130 nm. As shown in FIG. 5B, ULK resin having M_(wr)=3,000 Dacompletely filled metal structures, even when the pitch between metalstructures was lower, about 80 nm, with no apparent defects or voids.Therefore, ULK resins with M_(wr)<30,000 Da result in substantiallydefect-free filled ULK-ILD over metal interconnects.

Example 2

Example 2 presents the selection of porogen to arrive at a predeterminedporosity of the ULK material. Table 1 presents formulation andcharacterization data of hybrid refill materials using a commerciallyavailable Si-based low Mw resin from JSR Corp., Sunnyvale, Calif. withvarious commercially available surfactants as porogens.

TABLE 1 Sam- Formulation Porogen Thickness Refractive ple (wt %) M_(wp)HLB (nm) Index Defects 1 JSR2015/Brij52 331 5.3 455 1.3456 N (75/25) 2JSR2015/Brij76 711 12.4 511 1.3189 N (80/20) 3 JSR2015/Brij78 1152 15.3575 1.314 Y (80/20) 4 JSR2015/Brij700 4670 18.8 625 1.3066 N (85/15) 5JSR2015/15-S15 721 15.4 590 1.3204 N (85/15)

The dielectric constant of sample 5 in Table 1 was found using ametal-insulator-semiconductor (MIS) structure to be 2.4. Since therefractive index is directly proportional to dielectric constant, sample5 was used as a benchmark for k=2.4 with a corresponding refractiveindex (RI) of 1.3204. As shown in Table 1, the porogen may have aM_(wp)>400 Da in order to have enough efficiency to arrive at thepredetermined refractive index and corresponding dielectric constant.

In order to achieve a defect free gap-fill, the porogen's M_(wp) and HLBmust be selected. FIG. 6 is a plot illustrating the porogen's M_(wp)versus HLB, and the selected processing windows for defect free gap-fillof 80 nm pitch metal structures. Window A, corresponds to samples usingporogens with a M_(wp)<400 Da, and as previously discussed, does not hitthe target dielectric constant regardless of HLB value. Window B,corresponds to samples using porogens with 400<M_(wp)<1000 Da, and isshown to produce defect free gap-fill for all HLB values. Window C,corresponds to samples using porogens with M_(wp)>1000 Da and HLBvalues >16, which also produce defect free gap-fill. Finally, window Dcorresponds to samples using porogens with M_(wp)>1000 Da and HLB values<16. Such systems produce incomplete gap-fill or void and defects withcritical dimensions greater than 5 nm.

Example 3

The effect of a combination UV/thermal cure of the hybrid material(resin and porogen) was compared with a thermal cure on the yield of asubstantially defect-free fully cured ULK-ILD material. An integratedcircuit substrate including metal structures with about 80 nm pitch wasfilled with resin having the composition of sample 5 of Table 1 and wasthermally cured by heating at a rate of 5° C./min from 50° C. to 450° C.The resin was allowed to soak into the metal structures at 450° C. forabout 60 minutes. FIG. 7A is a scanning electron microscopy image ofmetal structures refilled using thermal curing. Defects such as voidsare observed in FIG. 7A. In contrast, a combination of UV radiation andthermal curing was found to result in a substantially defect-free cureddielectric material, as shown in FIG. 7B. FIG. 7A is a scanning electronmicroscopy image of metal structures refilled using combinationUV/thermal curing. A resin having the composition of sample 5 of Table 1was filled in metal structures with a pitch of 80 nm and was cured for300 seconds at 400° C. The wavelength of the UV radiation was 100 to 400nm.

Altogether, these results show that one or more of selected values ofM_(wr), M_(wp), HLB, and combination UV/thermal curing can be used toobtain substantially defect-free cured ULK-ILD in patterned metal linesin integrated circuit substrates.

Various examples of the invention have been described. These and otherexamples are within the scope of the following claims.

The invention claimed is:
 1. A method comprising: depositing a fillingmaterial onto a structure comprising a patterned metal on a surface of asubstrate, the patterned metal comprising metal features separated bygaps, the gaps having an average gap dimension of less than about 100nm, wherein the filling material comprises a silicon-based resin havinga molecular weight of less than about 30,000 Da and a porogen having amolecular weight greater than about 400 Da; treating the depositedfilling material in a first thermal treatment to substantially fill allgaps with the filling material; and treating the deposited fillingmaterial in a second thermal treatment, and applying a UV radiationtreatment to the deposited filling material, thereby crosslinking thesilicon-based resin and decomposing the porogen, thus forming a porouslow dielectric constant material having a dielectric value of less thanabout 2.7, wherein an interfacial region between the metal features andthe porous low dielectric constant material comprises less than about0.1% by volume of voids after one or both of the second thermaltreatment and the UV radiation treatment.
 2. The method of claim 1,wherein the second thermal treatment and the UV radiation treatment aresimultaneous for at least a predetermined time duration.
 3. The methodof claim 2, wherein the predetermined time duration comprisessubstantially an entire duration of the second thermal treatment.
 4. Themethod of claim 2, wherein the predetermined time duration comprisessubstantially an entire duration of the UV radiation treatment.
 5. Themethod of claim 1, wherein the porogen has an HLB(hydrophilic-lipophilic balance) value greater than about
 16. 6. Themethod of claim 5, wherein the porogen has a molecular weight greaterthan about 1000 Da.
 7. The method of claim 1, wherein the first thermaltreatment comprises heating the deposited filling material to atemperature from about 75 to about 250° C. for a time from about 1minute to about 30 minutes.
 8. The method of claim 1, wherein the secondthermal treatment comprises heating the thermally treated depositedfilling material to a temperature in the range of about 300° C. to about500° C. for a time from about 1 minutes to about 120 minutes.
 9. Themethod of claim 1, wherein the UV radiation treatment comprises exposingthe filling material to radiation of a wavelength from about 100 toabout 400 nm for a time from about 30 seconds to about 600 seconds. 10.The method of claim 1, wherein the interfacial region is substantiallyfree of voids.
 11. The method of claim 1, wherein a maximum criticaldimension of the voids is less than about 5 nm.
 12. The method of claim1, wherein the depositing the filling material comprises spin-on coatingof the filling material onto the patterned metal.
 13. The method ofclaim 1, wherein the filling material comprises less than or about 50 wt% of the porogen.
 14. A method of filling gaps in a patterned metalstructure, the gaps having a critical dimension of less than 100 nm, themethod comprising: depositing a filling material onto the structure,wherein the filling material includes (i) a silicon-based resin that hasa molecular weight of less than 30,000 Daltons, and (ii) a porogenhaving a molecular weight of greater than 400 Daltons; subjecting thedeposited filling material to a post-apply thermal treatment; andexposing the thermally treated, deposited filling material to both UVradiation and heat, thereby both crosslinking the silicon-based resinand decomposing the porogen, to form a low dielectric constant material(k<2.7) that fills the gaps.
 15. The method of claim 14, wherein duringsaid exposing, the filling material is heated to a temperature in therange of approximately 200° C. to 500° C.
 16. The method of claim 14,wherein no voids within the filled gaps are created that have a criticaldimension greater than 5 nm.
 17. The method of claim 14, wherein thestructure has a pitch of less than 100 nm.
 18. The method of claim 14,wherein the porogen has a molecular weight of greater than 1000 Daltons,and wherein the porogen has an HLB value of greater than 16.